The ornamental design for a displayscreen or portion thereof with transitional graphical user interface, as shown and described.
FIG. 1 is a front view of a first image in a sequence according to a first embodiment of our design for a display screen or portion thereof with transitional graphical user interface;
FIG. 2 is a front view of a second image in the sequence thereof;
FIG. 3 is a front view of a first image in a sequence according to a second embodiment of our design for a display screen or portion thereof with transitional graphical user interface; and,
FIG. 4 is a front view of a second image in the sequence thereof.
The appearance of the claimed design transitions between the images shown in FIGS. 1 to 2 and between the images shown in FIGS. 3 through 4. The process or period in which one image transitions to another forms no part of the claimed design.
The outer broken line rounded rectangles showing a device, the broken line rectangle showing the display screen or portion thereof, and all other broken lines showing portions of the graphical user interface form no part of the claimed design.